Definition: Set of disruptive abnormalities, including lateral body-wall defect involving thorax, abdomen or both, skeletal abnormalities of the spine, lower or upper limb reduction anomalies and a failure of umbilical cord development1.

Incidence: 0.7:10,0002.

Etiology: Unknown. Some authors believe in the impact of a yet unrecognized teratogen3,4. The abuse of cocaine has recently been associated with the development of the limb-body wall complex 5.

Pathogenesis: Body stalk anomaly is a part of the Early amnion rupture sequence (as result of compression or vascular disruption) or results from a defect in the germ disc, leading to an abnormal body folding and faulty fetal morphogenesis.

Introduction

Body folding, as a result of the rapid growth of the embryo and particularly of the nervous system, occurs mainly in the 4th-5th embryologic week. The head-, tail-, and the two lateral folds separate the intra- from the extraembryonic coelom, creating the formation of a primitive gut and the anterior part of the diaphragm. The body stalk, now positioned at the ventral part of the embryo, elongates to form the umbilical cord and will be covered by the amnion. The amnio-embryonic transition is reduced to a narrow region at the umbilical site on the ventral body surface. Errors in body folding occur sporadically, leading to severe, often lethal malformations of which the complexity largely depends on the involvement of each of the body folds.

This case report illustrates the sonographic and pathologic findings in a large body stalk malformation and gives a short review of the literature.

Case report

An ultrasound scan was performed in a G1P0 woman at 19 weeks of gestation. Fetal biometry was within normal ranges. A complex fetoplacental malformation pattern was observed. A scalloping of the frontal bones (lemon sign) was observed, with a thickening of the nuchal fold (7mm). The fetal intracranial structures demonstrated no other anomalies. The small thorax and the absence of the diaphragm resulted in a thoracoabdominal shifting and marked levorotation of the fetal heart (fig. 1).

Figure 1: Transverse section through the lower part of the thorax. A large abdominal wall defect resulting in a small thoracic diameter and thoracoabdominal cardiac shift. (S=spine, h= shifted heart, v=herniated viscera).

No cardiac malformations were visualized. A huge abdominal wall defect, extending from the distal part of the sternum to the suprapubic region, caused the evisceration of the fetal liver, stomach and intestines (fig. 1). A rather short umbilical cord connected the fetus tightly to the placenta (fig. 2).

Figure 2: The short umbilical cord connects the fetus to the placenta. Transverse section at the level of the bladder. (p=placenta, b= bladder, c=cord).

Liver and intestines were freely floating in a large amount of amniotic fluid. They were covered by a tiny membrane starting off from a broad abdominal ring delineated by the inferior sternal border and the suprapubic region, to reach the placental border. Both kidneys were normally developed but drained into an extrophied bladder (fig. 3).

Figure 3: The bladder opens directly in the abdominoperitoneal membrane. Transverse section through the lower part of the abdomen (s=spine, p=placenta, b= bladder).

The fetal spine showed a complex torsion at the thoraco-lumbar level, resulting in an extreme abnormal positioning of the left leg at the femur-pelvis articulation. A rockerbottom foot was present at the left leg. At the caudal end of the spine, a small skin covered neural tube lesion was observed (fig. 4). The fetal sex could not be determined. The placenta was of the circumvallate type. Fetal blood sampling revealed a normal male karyotype and a normal biology. Amniotic fluid alpha-fetoprotein concentration was 134,700 kU/L (median = 6,000 kU/L), The couple opted to terminate the pregnancy.

Figure 4: A closed spinal defect is observed at the lumbosacral region (arrow).

Autopsy

Pathologic examination (fig. 5) confirmed the diagnosis of a body stalk malformation. The circumvallate placenta was connected with a short broad umbilical cord to the fetal abdomen. The amnion extended from the placental ridge to the border of the huge abdominal wall defect, which reached from the distal part of the sternum to the suprapubic region (fig. 5).

Figure 5: The pathological examination confirms the large abdominal wall defect, the close relationship of the fetus to the placenta, the kyphoscoliosis of the spine and the abnormal position of the legs.

This pseudo-sac contained the fetal intestines and liver, bathing in amniotic fluid, draining from the exstrophied bladder. The diaphragm was lacking. Further inspection showed a Potter-like facies, a small bell-shaped thorax and an extreme torsion and scoliosis of the spine, The right leg was much smaller and presented a flexion contracture of the knee joint. The left leg showed a rockerbottom foot. The colon ended blindly in a large meconium-filled pouch; there was an anal atresia. Both kidneys were fused. The ureters drained into a rudimentary bladder, which opened into the amnioperitoneal sac. A fetal X-ray (fig. 6) highlighted the spinal scoliosis and rotation, the hemivertebrae at the lumbal site, the rockerbottom foot and the underdeveloped right leg.

Figure 6: The X-ray examination demonstrates the spinal kyphoscoliosis and the hypoplasia of the thorax. The lumbosacral part of the spine is composed of hemivertebrae. The legs have developed unequally and are malpositioned.

Discussion

Definition

Body stalk anomaly represents a set of disruptive abnormalities having in common the failure of closure of the ventral wall, characterized by a severe body-wall defect (thorax, abdomen or both), evisceration of the abdominal organs into an amnioperitoneal sac and a shortened or absent umbilical cord. There is also a failure of fusion of the amnion and chorion.

Incidence

The incidence of limb-body wall complex is 1:14,273 births2. There is no sex prediliction. The risk of recurrence is negligible7.

Etiology

The etiology of the body stalk malformation is not known.

Pathogenesis

The pathogenesis of body stalk anomaly is uncertain. Two major hypotheses are currently formulated.

·Body stalk anomaly is a part of the Early Amnion Rupture Sequence and results from an early rupture of the amnion and mechanical compression between the 3-5th embryonic week7,8.

·Other authors favor the vascular disruption theory3. This theory explains some of the similar features observed in the amniotic band syndrome (limb amputations).

The body stalk malformation results from a defect in the germ disc, leading to an abnormal body folding, an abnormal amniotic cavity formation and a failure to obliterate the extraembryonic coelom. This accounts for the short or absent umbilical cord and the broad insertion of the amnio-peritoneal membrane onto the placental chorionic plate8,9. ­Cephalic body fold defects lead to an anterior diaphragmatic hernia, ectopia cordis, sternal cleft, cardiac defects and an upper midline omphalocele as observed in the Pentalogy of Cantrell10. Closing failure of the caudal body fold results in exstrophy of the bladder, imperforate anus, partial colonic agenesis and agenesis of one umbilical artery together with a hypogastric omphalocele. Aplasia or hypoplasia of the paraspinous or thoracolumbar musculature is responsible for the severe scoliosis. Insufficiency in both cephalic and caudal body folding leads to a combination of the above-mentioned features as depicted in our case report.

Diagnosis

The combination of a large abdominal wall defect with protrusion of the viscera, a severe spinal scoliosis, and a continuous juxtaposition of the fetus to the placenta may lead to the diagnosis1. Associated malformations include central nervous system lesions, cardiac malformations, urogenital anomalies, midfacial clefts, limb defects, amniotic bands and placental abnormalities3 (Table 1). Association with very high maternal serum- and amniotic fluid alpha-fetoprotein has been reported2,11. A second trimester diagnosis is possible, especially with transvaginal examinations.

Differential diagnosis

Differentiation of limb-body wall (Table 3) complex from early amnion rupture sequence is the most difficult. However, the limb deformities encountered in the early amnion rupture sequence are more frequently amputations and constrictions7; moreover, this condition lacks the internal malformations often observed in the body stalk malformation12. The association with kyphoscoliosis and short umbilical cord favors the diagnosis of body stalk anomaly6,9. In gastroschisis there is paramedian abdominal wall lesion, through which the intestines and/or liver protrude into the amniotic fluid. There is no covering membrane and the umbilical cord inserts at its normal position3. The omphalocele is a median herniation of the intestines into the umbilical cord. The intestines are surrounded by amnion, and the cord vessels well up from the top of the lesion. Chromosomal defects and cardiac malformations are frequently associated13.